Serum CETP status is independently associated with reduction rates in LDL-C in pitavastatin-treated diabetic patients and possible involvement of LXR in its association.

Abstract

BackgroundStatins decrease cholesteryl ester transfer protein (CETP) levels, which have been positively associated with hepatic lipid content as well as serum low density lipoproteins-cholesterol (LDL-C) levels. However, the relationship between the CETP status and statin-induced reductions in LDL-C levels has not yet been elucidated in detail. We herein examined the influence of the CETP status on the lipid-reducing effects of pitavastatin in hypercholesterolemic patients with type 2 diabetes mellitus as well as the molecular mechanism underlying pitavastatin-induced modifications in CETP levels.MethodsFifty-three patients were treated with 2 mg of pitavastatin for 3 months. Serum levels of LDL-C, small dense (sd) LDL-C, and CETP were measured before and after the pitavastatin treatment. The effects of pitavastatin, T0901317, a specific agonist for liver X receptor (LXR) that reflects hepatic cholesterol contents, and LXR silencing on CETP mRNA expression in HepG2 cells were also examined by a real-time PCR assay.ResultsThe pitavastatin treatment decreased LDL-C, sdLDL-C, and CETP levels by 39, 42, and 23 %, respectively. Despite the absence of a significant association between CETP and LDL-C levels at baseline, baseline CETP levels and its percentage change were an independent positive determinant for the changes observed in LDL-C and sdLDL-C levels. The LXR activation with T0901317 (0.5 μM), an in vitro condition analogous to hepatic cholesterol accumulation, increased CETP mRNA levels in HepG2 cells by approximately 220 %, while LXR silencing markedly diminished the increased expression of CETP. Pitavastatin (5 μM) decreased basal CETP mRNA levels by 21 %, and this was completely reversed by T0901317.ConclusionBaseline CETP levels may predict the lipid-reducing effects of pitavastatin. Pitavastatin-induced CETP reductions may be partially attributed to decreased LXR activity, predictable by the ensuing decline in hepatic cholesterol synthesis.Trial registrationUMIN Clinical Trials Registry ID UMIN000019020